1. Field of the Invention
The present invention relates to a system and a process for moulding plastics materials.
Conventionally, an injection nozzle for moulding plastics materials has a cylindrical steel core forming a central longitudinal injection passage for injecting the melted plastics material through one or more injection apertures into a moulding cavity of a mould. An electrical resistance is also wound spirally around the cylindrical core to heat the plastics material passing through the injection passage. The windings of the resistance are usually closer together in the area near the injection aperture, which is closer to the moulding cavity and therefore tends to cool more rapidly than the central areas of the nozzle.
2. Description of the Related Art
EP 1 231 041 describes an example of an injection nozzle for moulding plastics materials which essentially has a cylindrical core, an injection passage and at least one seat formed in the outer lateral surface of the cylindrical core to house at least one resistance element. The resistance element extends to a point near the lower end of the cylindrical core. The nozzle also has a steel body which is essentially in the form of a cup open at the lower end of the cylindrical core, having an inner surface congruent with the inner lateral surface of the core, and having surfaces forming end portions of the injection channel near the injection passage.